1. Field of the Invention
This invention relates to a radiation image read-out apparatus. This invention particularly relates to a dust removing mechanism in a radiation image read-out apparatus.
2. Description of the Prior Art
There have heretofore been known radiation image read-out apparatuses. With the radiation image read-out apparatuses, radiation image information of an object, such as a human body, is recorded on a stimulable phosphor sheet, which comprises a substrate and a layer of a stimulable phosphor overlaid on the substrate. The stimulable phosphor sheet, on which the radiation image information has been stored, is then exposed to stimulating rays, such as a laser beam, which cause it to emit light in proportion to the amount of energy stored thereon during its exposure to radiation. The light emitted by the stimulable phosphor sheet, upon stimulation thereof, is guided by a light guide member, which is associated with a mirror, and the guided light is photoelectrically converted into an image signal. The stimulable phosphor sheet, from which the image signal has been detected, is then exposed to erasing light, and energy remaining on the stimulable phosphor sheet is released.
The image signal having been obtained with the radiation image read-out apparatuses is subjected to image processing, such as gradation processing or processing in the frequency domain, and a processed image signal is obtained. The processed image signal is utilized for reproducing a visible image on film, a cathode ray tube (CRT) display device, or the like. The stimulable phosphor sheet, which has been erased, can be utilized again for recording radiation image information.
Ordinarily, the radiation image read-out apparatus having the constitution described above is positioned in a light-blocked location (hereinbelow referred to as the light-blocked room), such that weak light emitted by the stimulable phosphor sheet can be guided by a light guiding system utilizing the light guide member, the mirror, and the like. However, the light-blocked room does not block flows of air. Therefore, for example, when the stimulable phosphor sheet is inserted into the light-blocked room and discharged from the light-blocked room, dust enters into the light-blocked room. Dust flutters in the light-blocked room due to movement of a scanning system, heat generated by the stimulating rays, and the like, and accumulates on upward-facing surfaces of the light guide member and the mirror with the passage of time.
Dust having accumulated on the light guiding system often adversely affects the operation for reading out the radiation image information. For example, in order for the light guiding efficiency to be kept high, the spacing between the light guide member and the mirror is set to be markedly narrow. When dust accumulates and grows on the upper surfaces of the light guide member and the mirror, dust projects laterally from edges of the upper surfaces of the light guide member and the mirror. As a result, the stimulating rays, which travel along the optical path between the light guide member and the mirror is intercepted by the projecting dust. In such cases, a predetermined amount of stimulation energy cannot be given to the stimulable phosphor sheet.
In order for the optical path of the stimulating rays to be prevented from being intercepted by dust accumulating on the light guide member and the mirror, the applicant proposed a radiation image read-out apparatus, wherein the inclination angles of the upper surfaces of the light guide member and the mirror are set at large angles, or auxiliary members having upper surfaces set at large inclination angles are located on the upper surfaces of the light guide member and the mirror, such that dust falling toward the upper surfaces of the light guide member and the mirror may not remain thereon and may fall downwardly. The radiation image read-out apparatus is disclosed in Japanese Unexamined Patent Publication No. 5(1993)-142685.
However, with the radiation imageread-out apparatus, wherein the inclination angles of the upper surfaces of the light guiding system are set at large angles, or auxiliary members are located on the light guiding system, dust cannot be perfectly prevented from accumulating on the light guiding system. Also, in the cases of dust, such as waste thread, which is markedly light in weight but has a certain length, it often occurs that dust clings so as to be threaded over between the light guide member and the mirror. In such cases, with the inclination of the upper surfaces of the light guide member and the mirror, dust cannot be caused to fall downwardly. Further, in cases where dust conveyed due to the conveyance of the stimulable phosphor sheet transfers and clings to downward-facing surfaces of the light guide member and the mirror, dust cannot be removed from the downward-facing surfaces of the light guide member and the mirror.
In order for such dust to be removed, it is necessary to perform the operations for disassembling the radiation image read-out apparatus to expose the surfaces to which dust clings, removing the dust, and then assembling the radiation image read-outapparatus. However,the operations for disassembling the parts, which have been adjusted and assembled accurately, and then assembling them again cannot be performed by the users. Also, considerable time and labor are required to perform re-adjustment.